Labile phosphate in flooded soil as influenced by mineral nutrition of rice plants
Titel:
Labile phosphate in flooded soil as influenced by mineral nutrition of rice plants
Auteur:
Alva, A. K.
Verschenen in:
Communications in soil science and plant analysis
Paginering:
Jaargang 15 (1984) nr. 2 pagina's 161-176
Jaar:
1984-02
Inhoud:
Labile phosphate in flooded soil, subjected to increasing levels of N, P, and K applications, was measured based on isotopic dilution technique (L-value) four times during rice growing period and at maturity in a growth chamber experiment. Labile P based on isotopic exchange technique (E-value) was also determined at the end of the experiment. The L-values in general were fairly steady, increasing, and decreasing, respectively, during 30 to 50 days, 51 to 80 days, and 81 to 150 days. Reactions at soil/root interface favoring anaerobic condition, and increasing microbes responsible for reducing ferric phosphate were attributed to cause an increase in labile P, thus was termed as crop induced P mineralization. The reoxidation of soil/root interface leading to oxidation of ferrous to ferric was thought to be responsible for P immobilization. The labile P status increased with increasing N or P application during the initial period. Later on until the mid growing period labile P status increased at an increasing rate with decreasing levels of N or P application. Following this period, however, the labile P tended to decrease until maturity in all treatments. Increasing K application, however, did not seem to have a definite influence on the labile P status. Total P uptake by rice plants was significantly related to the E-values but not the L-values. The L-values were higher than the E-values and the relationship between these two measures was poor, thus suggesting that the L-and E-values cannot be treated as alternative measures of the labile P in flooded soil.
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